At the end of april, mandy told bill that she has read 16 books this year and reads 2 books each month. bill wants to catch up to mandy. he tracks his book reading with a table on his door. using his table below, what month will bill have read the same amount of books as mandy?

month books
may- 4
june- 8
july- 12

answer choices:
a. september
b. october
c. august
d. december